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\f0\b\fs24 \cf0 Global Warming Has Made California\'92s Drought Worse
\b0 \
by Kevin Fahey and Evan Sernoffsky\
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\cf0 Aug. 20, 2015 \'96 Human-caused global warming has made California\'92s 4-year drought worse and \'93substantially increased\'94 the likelihood of extreme dry spells from now on, scientists concluded, in 1 of the most detailed climate-change studies to date.\
The bottom line of the report, published Thursday in the journal
\i Geophysical Research Letters
\i0 , is that the Earth being hotter than normal makes the soil, and all that grows in it, drier than normal \'97 which then makes droughts worse than normal.\
Researchers have long tied California\'92s drought to an unusually stubborn ridge of high pressure, dubbed the \'93Ridiculously Resilient Ridge\'94 by one Stanford University scientist. It has hung over the Pacific Ocean, deflecting rainstorms away from the West Coast.\
It has been unclear, though, whether climate change is reinforcing that high-pressure system or contributing to the drought on its own. The study says climate change is probably not the cause of the high-pressure system \'97 but whenever heavy rain returns, evaporation caused by global warming will undercut its benefits.\
Thursday\'92s wide-ranging study, written by climate scientists from Columbia University and the University of Idaho, concludes that, by the 2060s, \'93more or less permanent drought will set in, interrupted only by the rainiest years.\'94\
\'93A lot of people think that the amount of rain that falls out of the sky is the only thing that matters,\'94 said lead author Park Williams, a bio-climatologist at Columbia\'92s Lamont-Doherty Earth Observatory. \'93But warming changes the baseline amount of water that\'92s available to us, because it sends water back into the sky.\'94 In other words, if the dirt and plants on the ground have been dried out by hotter temperatures, there is less water all around. Then the deficit of water that is called drought is worsened.\
The researchers concluded that climate change was responsible for 15 to 20% of the deficit in soil moisture in California from 2012 to 2014.\
Several studies in recent years have sought to identify whether climate change was the cause of the drought. Thursday\'92s report is the 1st to quantify in such detail the extent to which global warming has worsened the drought. Researchers looked at month-by-month statistics from 1901 to 2014 at 24,000 locations in California, analyzing rainfall, temperature, humidity, wind and other data.\
The study makes clear that the lack of rain from \'93natural variability\'94 is the driving force behind the drought, but it found that global warming has increased the likelihood of \'93extreme California droughts.\'94\
Noah Diffenbaugh, editor in chief of
\i Geophysical Research Letters
\i0 , said the paper was \'93definitely the most comprehensive analysis of the historical record that I\'92ve seen.\'94 A senior fellow at Stanford\'92s Woods Institute for the Environment, Diffenbaugh led 2 studies over the past year that came to similar conclusions with fewer statistics.\
\'93If this drought was a one-off event, we could get through it and get on to the next times,\'94 he said. \'93But the research shows this is not the case. We are in the new normal, which means we will have more droughts than we did before.\'94\
Gov. Jerry Brown hailed the new report as justification for reforms to combat human-caused climate change. In April, he issued an executive order to reduce greenhouse gas emissions in California to 40% below 1990 levels by 2030. \'93It\'92s time for Republicans, foot-dragging corporations, and other deniers to wake up and take sensible action before it\'92s too late,\'94 Brown said.\
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\cf0 www.sfgate.com/news/article/Study-Global-warming-has-made-Calif-drought-6455565.php}